refactor: dfpath pkg

[gaius-qi]

Description

• Refactor dfpath pkg.

Related Issue

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist:

• Code compiles correctly.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-commenter]

Codecov Report

Merging #879 (3c49928) into main (f0f4d6c) will increase coverage by 41.39%.
The diff coverage is 44.00%.

@@            Coverage Diff            @@
##           main     #879       +/-   ##
=========================================
+ Coverage      0   41.39%   +41.39%     
=========================================
  Files         0      106      +106     
  Lines         0     8255     +8255     
=========================================
+ Hits          0     3417     +3417     
- Misses        0     4394     +4394     
- Partials      0      444      +444     

Flag	Coverage Δ
unittests	41.39% <44.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
client/config/dfget.go	23.52% <ø> (ø)
client/config/peerhost.go	35.29% <ø> (ø)
client/daemon/daemon.go	5.59% <0.00%> (ø)
manager/config/config.go	0.00% <ø> (ø)
pkg/source/plugin.go	0.00% <0.00%> (ø)
pkg/source/source_client.go	1.98% <0.00%> (ø)
scheduler/config/config.go	4.81% <ø> (ø)
scheduler/core/evaluator/evaluator.go	71.42% <0.00%> (ø)
internal/dfpath/dfpath.go	48.38% <48.38%> (ø)
client/config/dynconfig.go	58.06% <66.66%> (ø)
... and 109 more